The present invention relates to a novel system for removing paint overspray from a paint spray booth. More particularly, the present invention relates to a fluid wash spray paint system that includes a plurality of paint spray booths, each having a fluid wash device to entrap paint overspray. The fluid wash devices are coupled to a common sludge removal system which removes the pain sludge from the fluid and then recycles the fluid to form a closed system.
Conventional spray paint booths normally include a water wash eliminator section which is designed to remove paint overspray generated in the painting process from the air in the booth. Normally, a booth exhaust fan is provided which draws the air and paint overspray through a cascade of water. The water cascade separates the paint overspray from the air, and the water and paint overspray is then channeled to a reservoir. Paint overspray normally floats on the water in the reservoir. This floating paint is then removed, either manually or mechanically, by some sort of skimming device.
One problem with that type of conventional water wash system is that the paint, becuase of its composition, remains tacky and will readily adhere to exposed surfaces of the system, including the walls of the reservoir. The accumulation of the paint overspray on the system is generally detrimental to its function, and therefore necessitates cleaning of the system at frequent intervals. Another problem with that type of conventional water wash system is that it is difficult to remove much of the paint overspray from the wash water. That problem diminishes, or prevents, the ability to recycle the water back through the water wash device for an extended period of time. The wash water must be changed at frequent intervals, creating significant waste water disposal problems and inefficient spray booth usage.
Other conventional water wash systems have interconnected a number of paint spray booths having water wash devices with a common reservoir. The wash water and paint overspray from each spray booth is routed to the common reservoir where the paint overspray is then skimmed, either mechanically or manually. In this type of conventional water wash system, it is known to add a chemical which enhances the floatation of the paint. By forcing more of the paint to float on the surface, in theory more of the paint can be removed by the skimming operation. However, in practice, the addition of the floatation chemical to the water created other problems. While the addition of the floatation chemical normally causes the paint overspray to float for a period of time, a portion of the paint always seems to settle to the bottom of the reservoir. This creates two types of paint that has to be handled. The floating paint has to be skimmed from the surface of the reservoir, and the settled paint has to be removed from the bottom of the reservoir in some other manner. Generally, such conventional water wash systems had no provision for easily removing the settled paint from the bottom of the reservoir. Therefore, at regular intervals, the settled paint had to be mechanically removed from the bottom of the reservoir. This generally required that the sytem be shut down during the cleaning operation, which interrupted the painting cycle.
Other conventional water wash systems have attempted to utilize various types of separators to separate the paint overspray from the water. Generally, such separators have been unsuccessful because of the problems created by the paint floating on the surface of the water and adhering to the structure of the separator, which decreased the efficient of the separator, and created the need for frequent cleaning.
One object of the present invention is to provide a fluid wash system in which the tackiness of the paint overspray is eliminated. This will prevent the paint overspray from adhering to the surfaces of the system.
Another object of the present invention is to provide a central system that utilizes a common pit, or reservoir, and includes a separator that is capable of separating the paint overspray from the fluid to create generally clean fluid.
Another object of the present invention is to provide a system that is capable of forcing the entrapped paint overspray to settle as sludge toward the bottom of a common sludge pit.
Yet another object of the present invention is to provide a system in which the settled sludge can be removed from the fluid in a form that is easily disposable.
According to the present invention, a fluid wash spray paint system including a plurality of paint spray booths is provided. Each paint spray booth includes a fluid wash device to entrap paint overspray in a moving fluid to remove the overspray from the booth. The system also includes a sludge pit for collecting the fluid and entrapped paint overspray from the plurality of spray booths. The system further includes means for introducing a sludge-producing agent into the fluid and entrapped paint overspray to cause the paint to settle as sludge to the bottom of the sludge pit. Means for separating and removing the settled sludge from the fluid is provided along with means for circulating the fluid and sludge from the bottom of the sludge pit through the centrifugal means and returning the fluid with the sludge removed to the sludge pit. The system further includes second means for circulating the fluid from the sludge pit through the plurality of fluid wash spray devices.
One feature of the foregoing system is that a sludge-producing agent is introduced into the fluid and entrapped paint overspray to cause the paint to settle as sludge to the bottom of the sludge pit. The sludge-producing agent also serves to eliminate the tackiness of the paint overspray. One advantage of this feature is that the paint overspray is converted to a form that is relatively easy to remove from the fluid and does not adhere to the surfaces of the system itself.
Another feature of the foregoing system is that centrifugal means for separating and removing the settled sludge from the fluid is provided. One advantage of this feature is that substantially all of the settled sludge, and consequently substantially all of the paint overspray, is separated and removed from the fluid. Another advantage of this feature is that the fluid can be recycled through the fluid wash devices to form a closed system. This permits the fluid to be reused over and over again without the necessity of disposing of the fluid at frequent intervals.
In preferred embodiments of the present invention, the system includes means for agitating the fluid and the settled sludge to keep the sludge partially suspended in the fluid near the bottom section of the sludge pit. One feature of the foregoing system is that the settled sludge is not allowed to accumulate in the bottom section of th sludge pit. One advantage of this feature is that the fluid and sludge are more easily pumped from the bottom section of the sludge pit to the centrifugal means.
Also in preferred embodiments of the present invention, at least one spray nozzle is positioned above the sludge pit and adapted to spray a portion of the circulating fluid onto the fluid and sludge in the sludge pit to prevent the formation of foam. One feature of the foregoing structure is that the circulating fluid is used to dissipate and prevent foam from the agitated fluid and sludge mixture in the sludge pit. One advantage of this feature is that it eliminates the necessity for introducing a separate defoaming chemical into the fluid to dissipate the foam.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of a prefered embodiment exemplifying the best mode of carrying out the invention as presently perceived.